CN1061700C - High-strength ferritic heat-resistant steel and process for producing the same - Google Patents

High-strength ferritic heat-resistant steel and process for producing the same Download PDF

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CN1061700C
CN1061700C CN95191368A CN95191368A CN1061700C CN 1061700 C CN1061700 C CN 1061700C CN 95191368 A CN95191368 A CN 95191368A CN 95191368 A CN95191368 A CN 95191368A CN 1061700 C CN1061700 C CN 1061700C
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steel
carbide
creep
strength
value
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CN1139459A (en
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藤田利夫
长谷川泰士
直井久
佐藤恭
田村広治
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Teng Tian
Nippon Steel Corp
Mitsubishi Power Ltd
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Teng Tian
Babcock Hitachi KK
Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
    • F28F21/081—Heat exchange elements made from metals or metal alloys
    • F28F21/082—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys
    • F28F21/083—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys from stainless steel

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

This invention provides a ferritic heat-resistant steel having excellent HAZ softening resistance characteristics and exhibiting a high creep strength up to a high temperature of not lower than 500 DEG C., and a method of producing such a steel, the steel comprising in terms of mass %, 0.01 to 0.30% of C, 0.02 to 0.80% of Si, 0.20 to 1.50% of Mn, 0.50 to 5.00% of Cr, 0.01 to 1.50% of Mo, 0.01 to 3.50% of W, 0.02 to 1.00% of V, 0.01 to 0.50% of Nb, 0.001 to 0.06% of N, one or both of 0.001 to 0.8% of Ti and 0.001 to 0.8% of Zr, wherein a value (Ti+Zr) in (Cr, Fe, Ti, Zr) of a M23C6 type carbide in the steel is 5 to 65%, and the present invention provides a method of producing the same.

Description

High-strength ferritic heat-resistant steel and manufacture method thereof
The present invention relates to a kind of jessop, particularly relate to and be used for high temperature and high pressure environment, the jessop of high creep-rupture strength and superior anti-HAZ softening properties is arranged.The present invention be more particularly directed to by control because carbide is constituted the intensity that the variation that heat effect produced of element produces and the improvement of toughness aspect.
Become the ground that attracts people's attention of temperature and pressure under the operational conditions of thermal boiler is high in recent years, and some boiler moves under 566 ℃ and 316 conditions of clinging to.Waiting in expectation in the future is up to 649 ℃ and 352 operational conditionss of clinging to, and will propose utmost point exacting terms to used material.
The high temperature steel that is used for heat power plant is exposed to different environment according to its used position.The ferrite material that has the austenite material of high-temperature corrosion resistance performance and extra high intensity and contain the Cr of 9-12% has been widely used in the position of high metal temperature, reaches " reheat organ pipe " as so-called " superheater tube ".
Recently developed and wherein added W again, and it has dropped into practical application and the high-level efficiency that reaches the power station has been contributed so that improve the high temperature steel of the novelty of hot strength.For example, the patent disclosure No.63-89644 of Japanese unexamined, 61-231139,62-297435 etc. disclose a kind of jessop, and it strengthens element and can make creep-rupture strength than the jessop that contains Mo of prior art surprising raising be arranged by adopting W to make sosoloid.Being organized in of these steel in most cases is single-phase tempered martensite, because the set with ferritic steel superiority of superior anti-steam oxidation ability and high-strength characteristic expects that then they become the follow-on material that is used for the high temperature and high pressure environment.
Because heat power plant has reached higher pressure, so present low relatively position of operating temperature, operational conditions as the wall pipe of roasting kiln, heat exchanger, vapour generator, main team pipe also becomes harsh, thereby by the jessop of the low Cr content of industrial standards regulation, as so-called " 1Cr steel ", " 1.25Cr steel ", " 2.25Cr steel " etc. then can not adapt to operational conditions.
For adapting to this trend, a large amount of, be suggested by adding the steel that W or Mo improved hot strength to these low-intensity materials energetically.In other words, Japanese unexamined patent publication No. is open, and patent announcement No.6-2926 that NO.63-18038 and 4-268040 and Japan have examined and 6-2927 have proposed by adding W as mainly strengthening the steel that element has improved the hot strength of 1-3%Cr steel.The hot strength of any in these steel is the height of conventional low Cr steel all.
On the other hand, these jessops have utilized ferritic structure, as martensitic stucture, Bainite tissue etc., or the high strength of its tempered structure, these tissues contain a large amount of dislocations, and the generation of described dislocation is owing to the result who adds the surfusion that the phase transformation of carbide precipitated phase demonstrates from single-phase austenitic area to ferrite who takes place in heat treated process of cooling.Therefore, when this tissue is subjected to reheating to the thermal hysteresis in austenite one phase district, as when being subjected to the influencing of welding heat, then highdensity dislocation is resumed again, thereby takes place easily at welded heat affecting zone that intensity is local to descend.Especially by reheating to the position that is higher than the ferritic-austenitic transition point temperature, those by reheating near the temperature of this transition point, as about 900 ℃ for the about 800-of 2.25%Cr steel, and then just become fine grain structure in the position of short period of time internal cooling, this is because before austenite crystal is fully grown diffusionless transformation has taken place, and changes as martensitic transformation or Bainite.Also have, because the restriction of the solid solution of the high C in γ district and N, as the M that improves the principal element of the strength of materials by precipitation hardening 23C 6The type carbide is being heated to above the temperature of transition point, even the short period of time also is converted into sosoloid very easily again.This M 23C 6The type carbide mainly is to separate out on the γ crystal boundary or on extremely thick insoluble carbide thickly.
Owing to the acting in conjunction of these mechanism makes the local phenomenon that descends of creep strength,, hereinafter will be referred to as " HAZ is softening " for for simplicity.
The present inventor has done abundant and detailed research to this softened zone, and finds: the decline of intensity is mainly due to M 23C 6The type carbide constitutes the change of element.Because further research, the inventor finds: a large amount of, for the particularly indispensable element of the solution hardening of high strength martensitic high temperature steel, Mo or W stand solid solution and become M 23C 6Formation metallic element M, and on the crystal boundary of fine grain structure, separate out, also find: the result produces to expose the phase of Mo or W near austenite grain boundary, thereby causes that creep strength is local to descend.
Therefore, the decline of the creep strength of bringing owing to the influence of welding heat is strict for high temperature steel, and prior art, can not address this problem to essence as the optimization of thermal treatment or weldprocedure.Also have, adopt to it is believed that it is unique terms of settlement, it is infeasible when considering the method for construction in power station that this weld is changed into austenitic completely measure again.Therefore, Chang Gui martensitic steel or ferritic steel unavoidably will be met this " HAZ is softening " phenomenon.
Thereby, though contain the novel low Cr jessop of W and Mo high matrix metal intensity is arranged, but they demonstrate again with matrix metal intensity and are in a ratio of up to 30%, the part that is positioned at the intensity at welded heat affecting zone place descends, therefore, be considered to by the little material of the improvement effect of prior art intensity.
For avoiding the problem of above-mentioned prior art steel, i.e. M 23C 6The decomposition of carbide reaches owing to the long local softening district that slightly forms welded heat affecting zone of crystal grain, and makes control M 23C 6The formation of type carbide and the size of precipitate become possibility, the invention provides the new jessop and the production method thereof that add W and Mo type.Target of the present invention is particularly in providing a kind of high-strength ferritic heat-resistant steel, and this steel is owing to contain a kind of among Ti and the Zr or two kinds, and because the combination of the production technique of regulation and do not produce " HAZ softened zone ".
The present invention finishes on the basis of above-mentioned discovery, and main points of the present invention are following each point.
A kind of jessop that good anti-HAZ softening properties is arranged, it contains (weight %):
C： 0．01-0．30％， Si：0．02-0．80％，
Mn:0.20-1.50%, Cr:0.50 is to less than 5.00%,
Mo：0．01-1．50％， W： 0．01-3．50％，
V： 0．02-1．00％， Nb：0．01-0．50％，
N： 0．001-0．06％，
No matter following column element is independent or bonded, in one or both:
Ti:0.001-0.8%, and Zr:0.001-0.80%;
P: be not more than 0.030%,
S: be not more than 0.010%,
O: be not more than 0.020%,
A kind of in the following column element or two kinds:
Co:0.2-5.0%, and Ni:0.2-5.0%,
And
The surplus that constitutes by Fe and unavoidable impurities;
Wherein, make M 23C 6The type carbide is separated out as its nuclear with the carbide of Ti and Zr, changes into by (Cr, Fe, Ti, Zr) as its main component by mutual solid solution then 23C 6The carbide that constitutes, and the value of (Ti%+Zr%) in (Cr, Fe, Ti, Zr) is 5-65.Main idea of the present invention also is the production method of the jessop of good anti-HAZ softening properties, this method is included in tapping and adds Ti and Zr immediately within preceding 10 minutes, so that the value of (Ti%+Zr%) in above-mentioned (Cr, Fe, Ti, Zr) becomes 5-65, after 880-930 ℃ solution heat treatment, temporarily stop cooling, and under same temperature, this steel is incubated 5-60 minute.
Fig. 1 has showed the end groove shape that is welded to connect the place.
Fig. 2 has showed the method for getting the precipitate analytical sample at welded heat affecting zone.
Fig. 3 shows the time add Ti and Zr and chart as the existence form of the Ti of precipitate in the steel and Zr.
Fig. 4 shows the temperature when carbide separate out is with the cooling time-out and the curve of the relation between the residence time.
Fig. 5 shows that HAZ place's precipitate form and cooling suspend the chart of the relation between temperature.
Fig. 6 shows matrix metal, poor D-CRS between this value of creep-rupture strength that 600 ℃, 100000 hours linear extrapolation is inferred and weld and the M in the welded heat affecting zone 23C 6Graph of a relation between (Ti%+Zr%) value M% in the type carbide.
Fig. 7 (a) and 7 (b) have showed the method for getting the sample of creep-rupture strength test from steel pipe and sheet material respectively.
Fig. 8 shows the rupture time of repture test and the curve of the relation between added stress.
Fig. 9 (a) and 9 (b) have showed the method for getting the creep rupture sample from steel pipe and sheet material respectively.
Figure 10 (a) and 10 (b) have showed the method for getting the charpy impact test sample from the weld of steel pipe and sheet material respectively.
Figure 11 is the figure that concerns between the creep-rupture strength calculated of the linear extrapolation of the matrix metal of showing 600 ℃, 100000 hours and (Ti%+Zr%) value in this matrix metal.
Figure 12 is the M that shows welded heat affecting zone 23C 6The figure of the relation between the M% value of (Ti%+Zr%) in the type carbide and the toughness of this weld.
Below will explain in detail the present invention.
At first explain the reason that each component is limited to above-mentioned scope.
C is that proof strength is necessary. If but its content is lower than 0.01%, then can not guarantee enough intensity, if it surpasses the 0.30% then obvious hardening of welding heat affected zone, thus cold cracking when causing welding. Therefore the scope that C content is limited to 0.01-0.30%.
Si guarantees oxidation resistance, and as the important element of deoxidier. If its amount is less than 0.02%, then this effect of Si is insufficient, and if it surpasses 0.80%, then creep strength decline. Therefore, the scope that Si content is limited to 0.02-0.80%.
Not only for deoxidation, and for guaranteeing that intensity Mn is necessary component. For reaching enough effects, need add at least 0.20% Mn. If but its amount is greater than 1.50% the time in some cases, creep strength descends. Therefore the scope that Mn content is limited to 0.20-1.50%.
Cr is the indispensable element that guarantees non-oxidizability, and simultaneously, when its with the base metal matrix in C and carefully precipitate with such as Cr23C 6、Cr 7C 3Etc. form in conjunction with the time also help to improve creep strength. For oxidation resistant purpose, will be defined as 0.5% under it, and be to guarantee under the room temperature enough toughness is arranged, be defined as less than 5.0% on it.
W obviously improves the element of creep strength by solution strengthening, and is in long-time, especially is being higher than the element that obviously improves creep strength under 500 ℃ the temperature. If but add W with the amount above 3.5%, then a large amount of W separates out as intermetallic compound centered by crystal boundary, thereby obviously reduces toughness and the creep strength of base metal. Therefore, its upper limit is decided to be 3.5%. If its amount is less than 0.01%, then the effect of solution strengthening is not enough. Therefore its lower limit is decided to be 0.01%.
Mo also is the element that improves elevated temperature strength by solution strengthening. If but its amount is less than 0.01%, then its effect is insufficient, and if its amount above 1.00%, then separate out a large amount of Mo2C type carbide or Fe2Mo type intermetallic compound, and add simultaneously fashionablely as Mo and W, the toughness of parent metal obviously descends in some cases. Therefore will be defined as 1.00% on it.
When V separated out as precipitate and together stand solid solution with W in matrix, it was the element that obviously improves the creep rupture strength at high temperatures of steel. If V is less than 0.02% in the present invention, then to separate out the precipitation strength of generation insufficient because of V, and opposite, if it surpasses 1.00%, then form V-type carbide or carbonitride bunch, thereby toughness is descended. Therefore V content is limit in the scope of 0.02-1.00%.
Its improves elevated temperature strength and helps solution strengthening during with MX type carbide or Carbonitride Precipitation as Nb. If its amount is then discovered less than the effect that adds V less than 0.01%, and if it surpasses 0.5%, then Nb separates out with big particle, thereby toughness is descended. Therefore its content is limit in the scope of 0.01-0.50%.
N is dissolved in the matrix as solid solution, or mainly separates out nitride or carbonitride with the form of VN and NbN or its carbonitride separately, thereby is conducive to solution strengthening and precipitation-hardening. If it is less than 0.001%, then N almost is helpless to strengthen, and according on be limited to 5% Cr addition consider its can be added in the molten steel upper in limited time, its upper limit is decided to be 0.06%.
Adding Ti and Zr is main idea of the present invention, be combined with new and specific production stage and adds these elements and just may avoid " HAZ softens ". In the components system of this steel, Ti and Zr have high and affinity C, as M23C 6The formation metallic element be solid-solubilized among the M and improve M23C 6Decomposition temperature (again solid solution point). Therefore, they are for the M that prevents in " HAZ is softening " district23C 6Chap is effective. In addition, they prevent that also solid solution becomes M to W with Mo23C 6 Thereby do not form around the W of this precipitate exposed mutually with Mo. These elements both can be individually, but also the two adds in combination, and their effect can be by 0.001% lower limit and obtain. Thereby owing to add these elements and form thick MX type carbide and impair toughness to surpass 0.8% amount with the form of one matter, so its content is limited in the scope of 0.001-0.8%.
P, S and O are the impurity in the steel of the present invention. Aspect effect of the present invention, P and S reduce intensity, and O separates out as oxide and reduce toughness. Therefore its higher limit is decided to be respectively 0.03%, 0.01% and 0.02%.
Said components is solvent of the present invention, but can add a kind of among the Ni of 0.2-5.0% and the Co and two kinds according to required purposes.
Ni and Co are strong austenite stabilizer element. Especially at a large amount of ferrite stabilizers that add, during such as Cr, W, Mo, Ti, Zr, Si etc., be to obtain iron plain sheet tissue, such as bainite and martensite or its tempered structure, Ni and Co are necessary, and under such occasion, they are useful. Meanwhile, Co is effective for improving intensity to Ni for improving toughness. If their amount is less than 0.2%, then this effect is not enough, and if above 5. 0%, then separate out inevitably thick intermetallic compound. Therefore the content with them is limited in the scope of 0.2-5.0%.
By the way, the invention provides the high-strength ferritic refractory steel with superior anti-HAZ softening properties. Therefore, can be according to the application target of steel of the present invention and it is adopted suitable production method and heat treatment, and effect of the present invention can not be subjected to their obstruction at all.
But in order suitably to bring into play the above-mentioned effect that adds Ti and Zr, be present in the M in the welding heat affected zone23C 6In the metal component of type carbide, that is, (Ti%+Zr%) value in (Cr, Fe, Ti, Zr) is necessary for 5-65. Therefore, for Ti and Zr are separated out in steel with suitable carbide morphology, add immediately in their before tapping 10 minutes, and need to separate out form by be incubated 5-60 minute control under same temperature in the time-out after the solution heat treatment under 880-930 ℃ temperature cooling and with steel, and utilization (Cr, Fe, Ti, Zr) is separated out as M when the follow-up temper as key component M23C 6The nuclear of precipitate. Only have and just suitably show the effect that adds Ti and Zr when stating production method on the implementation, and just can finish purpose of the present invention whereby. In other words, even the chemical composition that material is contained is transferred in the scope of the present invention, and it is only used the production method of conventional steel, then can not get the contemplated effect of the present invention. In other words, be present in M in the welding heat affected zone23C 6In the metal component of type carbide, namely (Ti%+Zr%) value in (Cr, Fe, Ti, Zr) can not be controlled as 5-65 with this technique.
The compositing range of this production method and above-mentioned carbide is by following experimental identification.
Will composition steel within the scope of the present invention melting in VIM (vacuum induction process furnace) and EF (electric furnace) except that Ti and Zr, be used as the continuous casting equipment casting of the used casting unit of common steel ingot then, this melting is if be necessary then to select AOD (argon-oxygen blowing Decarburising and refining equipment), VOD (vacuum suction oxygen decarburization equipment) and LF (ladle refining equipment) refining.Under the situation of continuous casting steel billet, it is made to the shape that the maximum cross-section is the plate slab of 210 * 1600mm, or makes the shape of sectional area than the former little square billet.Under the situation with common steel ingot casting equipment casting, foundry goods is made to the ingot shape of various size.After this, they are forged, and get the suitable sample of size for follow-up study.
Add Ti and Zr in the various moment, promptly when the melting with VIF or EF begins, in fusion process, finished melting preceding 5 minutes, when refinings such as AOD, VOD, LF begin and refining process finish and added Ti and Zr in preceding 10 minutes so that the different interpolation of test basis is constantly and the composition of the precipitate of the product after casting and to the influence of its shape.
It is long that each piece slab ingot is cut into 2-5mm, makes the plate of thick 25.4mm again, so that with 1100 ℃ maximum heating temperature, 1 hour residence time is carried out solution heat treatment.In follow-up process of cooling, under each temperature of 1080 ℃, 1030 ℃, 980 ℃, 930 ℃, 880 ℃ and 830 ℃, stop cooling, the longest stand-by time is 24 hours, remain on then in the identical furnace temperature, behind the air cooling, the detection of the residue extraction and analysis by carrying out precipitate with the transmission electron microscope that is provided with X-ray microcell quantitative analysis instrument and the form of precipitate.And then, every block of slab of gained is done 780 ℃, 1 hour tempering, then by form groove angle be 45 °, V-arrangement end bevel for welding (being shown in Fig. 1) carries out welding test.
Weld by TIG, and the employing of hot initial conditions is normal 15000J/cm concerning jessop.650 ℃, 6 hours supplemental heat processing is done to each welded sample that obtains in this wise in the welding back, gets the sample that extracts resistates analytical sample and transmission electron microscope with the method shown in Fig. 2 from the HAZ of each welded sample then.In the figure, label 9 refers to by the weldering metal, and label 10 refers to welded heat affecting zone, label 11 and refers to the block sample that extracts residue analysis, and label 12 refers to the sampling point of the sample on the thin film disk of transmission electron microscope.Fig. 3 shows the chart that concerns between the Ti that is present in the place, heat affected zone after the moment add Ti and Zr and the welding and Zr precipitate form, is understandable that, plays M for Ti and Zr are separated out 23C 6The effect of separating out core and at this M 23C 6Formation metallic element M in carry out solid solution, Ti and Zr must exist as very thin carbide earlier, and for this reason, they must be to add under the condition of low oxygen concentration, that is, in VOD or LF refining process, begin to add in preceding 10 minutes and be more preferably at continuous casting.When the Ti before detecting welding and the size of Zr precipitate, find to be about 0.15 μ m as this mean sizes of carbide with electron microscope.The average particulate diameter of this precipitate shown in Figure 3 is represented the result of the precipitate in this weld affected zone after welding supplemental heat in the welded heat affecting zone and follow-up is handled.
Fig. 4 be show that cooling after the solution heat treatment stops temperature and residence time and the carbide size separated out between the chart that concerns.In the case, this production method is limited to EF-LF-CC.The carbide size minimum of being separated out when cooling stops with 880 and 930 ℃ retention temperature is separated out and can define heavily under 5-60 minute residence time.Can determine that equally, in the case this mean sizes can be minimum.
Confirm that with the quantitative x-ray analysis instrument of microcell the composition of this carbide is the MX type carbide that mainly is made of Ti and Zr.Fig. 5 has showed that the cooling that stops the refrigerative processing step after the form of this precipitate and composition and the solution heat treatment at various temperatures stops the relation between temperature, each sample insulation 30 minutes, with this sample of air cooling, in 750 ℃ with this sample tempering, and then weld and the supplemental heat of postwelding is handled.The thinnest precipitate form was arranged before temper, play M 23C 6This carbide of separating out central role and the temper process in the M that separates out 23C 6Stand solid solution together, become M at last 23C 6The type carbide.Find Ti and to be sosoloid as Zr exist with the ratio of the 5-65 among this formation metallic element M.
Fig. 6 shows the M that is present in the welded heat affecting zone 23C 6The chart of relation between the poor D-CRS (MPa) between the creep-rupture strength of the M% value of the Ti%+Zr% in the type carbide and the creep-rupture strength of welded heat affecting zone and matrix metal part.When M% was between 5-65, the creep-rupture strength of welded heat affecting zone was compared the 7MPa that at most only descends with the creep-rupture strength of base metal part.Because this difference within the error of the 10MPa of the data of the creep-rupture strength of base metal, no longer manifests the HAZ ruckbildung that causes because of the precipitate decomposition so imagine this welded heat affecting zone.With the common M that mainly constitutes with Cr 23C 6Compare, in constituting metallic element M, contain the Ti of 5-65% and the M of Zr 23C 6The type carbide has higher decomposition temperature, even and be subjected to the influence of welding heat, it also more is difficult to be agglomerated into thick particle.In addition, can reach a conclusion: because on chemical affinity aspect and the phasor as can be known: replace Ti and Zr, or except that Ti and Zr, W and Mo are difficult to carry out solid solution, so found above-mentioned experimental result.
The present invention prepares the method for jessop, may further comprise the steps: add Ti and Zr individually or in combination in preceding 10 minutes in tapping, its amount is respectively in the scope of 0.001-0.8%, by normal casting, rolling or forge step after solution heat treatment after, suspend cooling in 880-930 ℃; And described steel kept 5-60 minute under same temperature.If do not use the production method of regulation of the present invention, even so when falling into the steel of the scope of the invention with common its chemical ingredients of method production, the carbide M in the heat affected zone, welding zone then 23C 6Composition anti-HAZ softening properties can not be provided.
Melting method for steel according to the invention does not have any restriction, can decide any in converter, induction heater, the arc-melting furnace etc. according to the cost to the chemical ingredients of this steel and used technology.Yet this melting technology must be provided with the hopper that can add Ti and Zr, wants in addition oxygen concn to be controlled to enough low concentration, so that at least 90% the separating out as carbide of these elements.Adopt to be provided with the LF that blows Ar equipment or electro-arc heater or plasma heater and to reduce oxygen concn in the molten steel for this reason, or handle with vacuum outgas that to reduce this concentration be effectively, and they have improved effect of the present invention.In the tubulation operation of rolling of the follow-up operation of rolling or production steel pipe, being intended to make the solution heat treatment of the solid solution homogenizing again of precipitate is necessary basically, and in process of cooling, can stop to cool off and keeping the equipment of temperature, it also is necessary more specifically saying so and the highlyest being heated to about 1000 ℃ stove.All, believed to producing the production method that steel according to the invention or steel work are effective or useful other all can suitably adopt as rolling, thermal treatment, tubulation, welding, cutting, detection etc., and they have no to hinder to effect of the present invention.
Particularly as steel tube producing method, employing makes steel form garden base or square billet, by hot extrusion or various seamless rolling method this base is processed into the method for seamless tube again, with hot rolling, cold rolling then-thin plate has the method for seam welding pipe again by the production of resistance welding formation pipe, the method for welding the production welded tube by TIG, MIG, SAW, LASER and EB all is possible, no matter is individually, or combination, as long as in the method for production technique according to the invention all is included in.In addition, after above-mentioned each method, carry out heat or warm fixed diameter rolling auxiliaryly, and add that various straightening technologies also are possible, and these class methods have further enlarged the size range in the use that meets steel of the present invention.
Steel according to the invention can various forms of slabs and thin plate provide, and can apply necessary heat treated sheet material to it and come to use by adopting with the shape of various heat-stable materials.This method can not have any influence to effect of the present invention.
Using HIP (hot isostatic pressing), CIP (isostatic cool pressing), powder metallurgy process, also is possible as sintering, handles the product that then can produce different shape by the elementary heat after the employing forming process.
The steel pipe of above-mentioned different shape, steel plate and heat-resistant piece can stand various thermal treatments according to purpose and purposes, and in order fully to show effect of the present invention, it is important that this class is handled.
Usually, it is to add tempering by normalizing (solution heat treatment) to handle and obtain product that a lot of situations are arranged, but can be individually or further adopt tempering again or normalizing in combination, and they also are useful.But stopping after the solution heat treatment cooled off and follow-up insulation is indispensable.
When N or C content are quite high, work as austenite stabilizer element, big as Co, Ni equal size, and when Cr equivalent value step-down, so-called " the subzero processing " that steel is cooled to below 0 ℃ to avoid keeping the austenite phase is available, and this method is effective for the mechanical characteristics of abundant acquisition steel according to the invention.
In the scope that material behavior can fully be showed, each in these technologies can repeatedly adopt, and such technology does not produce any influence to effect of the present invention.
In other words, can suitably select above-mentioned technology, and use it in the production technique of steel according to the invention.
Embodiment
With table among the 1-4 listed 300 tons, 120 tons, 60 tons, 300 kilograms, 100 kilograms and the 50 kilograms steel that does not add Ti and Zr of the present invention with common blast furnace-converter converting process, VIM, EF or the melting of laboratory vacuum melting equipment, usefulness is equipped with the electric arc reheater again, with the LF equipment that can blow Ar, or with the small-sized regeneration that suitable capacity is arranged produce that ingot is cast in the testing installation refining again and.Added a kind of among Ti and the Zr or two kinds in preceding 10 minutes in casting beginning,, then obtain slab or spindle so that adjust chemical ingredients.All be processed into thick plate of 50mm or the thick thin plate of 12mm with every kind in the gained slab, or be processed into the garden base through hot rolling.Through seamless rolling with each external diameter 74mm, the pipe of thick 10mm forms external diameter 380mm and the pipe of thick 50mm.In addition every kind of thin plate electric welding is obtained external diameter 280mm, the electric welding of thick 12mm is taken over.
Figure 9519136800151
D-CRS: the matrix metal and the quilt of being inferred by linear extrapolation weld between the position, 550 ℃, 100000 hours creep-rupture strength poor (MPa) HAZCRS: the weld of inferring by linear extrapolation, 550 ℃, 100000 hours creep-rupture strength (MPa).M%: the M in the welding heat affected position 23C 6(Ti%+Zr%) value M% (%) in the type carbide
Figure 9519136800191
D-CRS: between matrix metal of inferring by linear extrapolation and weld 550 ℃, 100000 hours creep-rupture strength poor (MPa) HAZCRS: 550 ℃, 100000 hours creep-rupture strength (MPa) M% of the weld of inferring by linear extrapolation: the M in the welded heat affecting zone 23C 6(Ti%+Zr%) value M% (%) in the type carbide
These all sheet materials and tubing are all through solution heat treatment.In 880-930 ℃ temperature range, suspend cooling, this steel work is kept 5-60 hour in stove after, carry out air cooling.Carry out 750 ℃ then, 1 hour temper.
On every block of sheet material, carry out the whole in advance processing in edge with the method very identical with Fig. 1, simultaneously with Fig. 1 in identical method form groove along garden Zhou Fangxiang at the pipe end of each pipe, garden week connect weldering with TIG or SAM welding carrying out pipe then.To 650 ℃, 6 hours softening annealing (PWHT) of each weld do.
For detecting the creep properties of matrix metal, under the situation of the tubing of Fig. 7 a from the position except that weld or welded heat affecting zone of steel pipe 1 along and the parallel direction of the axle of pipe 1 downcut the creep sample 5 of diameter 6mm, and under the situation of the sheet material shown in Fig. 7 (b), then cut sample 5 along the rolling direction of sheet material 3.550 ℃ of creep-rupture strengths of measuring each sample, then the linear extrapolation of gained data is obtained 100000 hours creep-rupture strength.
Fig. 8 shows the creep-rupture strength measuring result of the matrix metal that reaches 10000 hours and the extrapolation line of inferring 100000 hours breaking tenacitys.What be appreciated that is.More conventional low alloy steel of the high temperature creep strength of steel of the present invention and 1-3%Cr-0.5-1%Mo steel be high.
For detecting the creep properties of weld, shown in Fig. 9 (a) along cutting the sample 5 of diameter 6mm to 7 parallel directions with steel shaft, or from cutting with bonding wire 6 vertical directions 7, with 550 ℃ breaking tenacity linear extrapolations to 100000 hour, so that with the creep properties comparison of matrix metal with estimate.After this, for the purpose of explanation the present invention, term " creep-rupture strength " will be represented 550 ℃, the breaking tenacity that 100000 hours linear extrapolation is inferred.The inferred value of the creep linear extrapolation breaking tenacity of matrix metal and weld poor, that is, (the creep rupture deduction intensity) of matrix metal-(intensity is inferred in the HAZ creep rupture), promptly D-CRS (MPa) is used as anti-" HAZ is softening " index of speciality.Though this D-CRS value is subjected to the influence with respect to the sampling direction of this sample of the rolling direction of creep rupture sample slightly, the experiment of preliminary experiment shows that it influences within 5MPa.Therefore, when D-CRS was not more than 5MPa, then the anti-HAZ softening properties of this this material of value representation was extremely superior.
As for the precipitate at HAZ position, then with Fig. 2 in identical method get each sample, with acid pasting residue is proposed then.At M 23C 6After being determined, determine composition among its M with microcell quantitative scanning x-ray analysis instrument.(Ti%+Zr%) value is expressed as M% at this moment, then estimates.On the basis of this experimental result, set judgement criteria so that the M% value must fall into the scope of 5-65.In other words, the M value is not more than 5 or be not less than at 65 o'clock, and then HAZ-CRS descends.
Carry out toughness test for the characteristics of Indirect evaluation precipitate.
Press shown in Figure 10 (a) from each steel pipe, or by the JIS No4. grooved Xia Shi sample that cuts 2mm-V shown in Figure 10 (b) from each sheet material upper edge and bonding wire 9 vertical directions, and with fused portion and the representative the highest sclerosis position of notch position as welding.50J when its judgement criteria being decided to be 0 ℃ by the assembling condition of supposing this heat-stable material.
In order relatively to estimate the steel that steel that those chemical ingredientss and the present invention be not inconsistent and those production methods and the present invention are not inconsistent with similar method.Chemical composition wherein and evaluation result, D-CRS, HAZCRS and M% list in the table 2.Relation between D-CRS and M% is shown among Fig. 6.
Figure 11 shows the creep-rupture strength of base metal and the chart of the relation between Ti%+Zr% wherein.Excessive Ti of adding and Zr then cause the precipitate chap.The creep-rupture strength of matrix metal itself decline as a result, impact value then descend, and finally the two all descends.
Figure 12 is the M that shows in the welded heat affecting zone 23C 6In the figure that concerns between the toughness in contained (Ti%+Zr%) value M% and this district.When the M% value surpasses 65, then precipitate chap descends thereby toughness occurs.Be understood that like this evaluation of estimate is lower than standard value 50J.The observed value of D-CRS, HAZCRS and M% is generally listed in table 2 and 4 in the mode of data.
In the compared steel shown in the table 5, the representative of 76 and No. 77 steel adds the example of Ti and Zr when fusing, although chemical ingredients drops in the scope of the present invention, final M% value is less than 5, thereby makes anti-HAZ softening power deterioration.78 and No. 79 steel representatives descend owing to adding the not enough M% value that makes of Ti and Zr, thus the example of anti-HAZ softening properties variation (D-CRS is at least 10MPa).In 80 and No. 81 steel, in No. 80 steel excess add Ti and in No. 81 steel excess add Zr.Thereby separate out thick carbide (in No. 80 steel is TiC, is ZrC in No. 81 steel) in a large number, so can not control the M in the welded heat affecting zone 23C 6Composition, this has caused anti-HAZ softening properties variation.No. 83 steel represent that to suspend the cooled residence time after the solution heat treatment long, that is, 240 minutes example, so precipitate chap, thus M can not be controlled 23C 6Composition, and anti-HAZ softening properties variation.The representative of No. 84 steel adds the W quantity not sufficient, thereby matrix metal and the example that all descended by the creep-rupture strength of welding zone.No. 85 excessive W that add of steel representative, the result separates out thick intermetallic compound in a large number at matrix metal and weld, thus the final example that descends of creep-rupture strength.No. 86 steel is represented Nb and V addition deficiency, thus the example that creep-rupture strength all descends in base metal and the weld.
Figure 9519136800231
Table 6
No D-CRS*1(MPa) HAZCRS*2(MPa) BASECRS*3(MPa) M％ Ti, the Zr joining day
76 28 95 121 2．1 During fusing
77 28 103 131 3．0 ＂
78 32 106 128 4．1 In the steelmaking process, tapped preceding 5 minutes
79 26 98 124 4．5 ＂
80 24 100 124 0．6 ＂
81 35 99 134 0．2 ＂
82 38 81 119 1．6 ＂
83 31 110 141 1．5 ＂
84 3 56 59 42．6 ＂
85 2 63 65 22．1 ＂
86 5 42 47 31．3 ＂
D-CRS*1: 550 ℃ of inferring of linear extrapolation, 100000 hours matrix metal and the creep-rupture strength between the welding zone poor (MPa)
HAZCRS*2: 550 ℃ of inferring of linear extrapolation, the creep-rupture strength of 100000 hours weld (MPa)
BASECRS*3: 550 ℃ of inferring of linear extrapolation, the creep-rupture strength of 100000 hours matrix metal (MPa)
M%: M in the welded heat affecting zone 23C 6(Ti%+Zr%) value M% in the type carbide
The present invention can provide good anti-HAZ softening properties and be shown in high creep-rupture strength under the high temperature that is not less than 500 ℃, thereby very big contribution has been made in industrial development.

Claims (3)

1. have the jessop of good anti-HAZ softening properties, it contains (weight %)
C： 0．01-0．30％，
Si：0．02-0．80％，
Mn：0．20-1．50％，
Cr:0.50-is less than 5.00%,
Mo：0．01-1．50％，
W： 0．01-3．50％，
V： 0．02-1．00％，
Nb：0．01-0．50％，
A kind of among the N:0.001-0.06%, the independent or following element of bonded or two kinds:
Ti:0.001-0.8% and Zr:0.001-0.8%:
P: be not more than 0.030%,
S: be not more than 0.010%,
O: be not more than 0.020%, and
The surplus that Fe and unavoidable impurities are formed,
Be that nuclear makes M wherein by carbide with Ti and Zr 23C 6The type carbide is separated out, and then converts it into by (Cr, Fe, Ti, Zr) by mutual solid solution 23C 6Be the carbide of main ingredient formation, and (Ti%+Zr%) in described (Cr, Fe, Ti, Zr) value is 5-65.
2. the jessop of good anti-HAZ softening properties is arranged, comprises (weight %):
C： 0．01-0．30％，
Si：0．02-0．80％，
Mn：0．20-1．50％，
Cr:0.50-is less than 5.00%,
Mo：0．01-1．50％，
W： 0．01-3．50％，
V： 0．02-1．00％，
Nb：0．01-0．50％，
N： 0．001-0．06％，
A kind of under the independent or bonded in the column element or two kinds:
Ti:0.001-0.8% and
Zr：0．001-0．8％；
In the following column element one or both:
Co:0.2-5.0% and
Ni：0．2-5．0％；
P: be not more than 0.030%,
S: be not more than 0.010%,
O: be not more than 0.020%, and
The surplus that Fe and inevitable impurity constitute; Be that nuclear makes M wherein by carbide with Ti and Zr 23C 6The type carbide is separated out, and changes into by (Cr, Fe, Ti, Zr) by mutual solid solution then 23C 6Be the carbide of main component formation, and the value of (Ti%+Zr%) in described (Cr, Fe, Ti, Zr) is 5-65.
3. according to the production method of the jessop of claim 1 or 2, it is characterized in that: add Ti and Zr individually or in combination in preceding 10 minutes in tapping, its amount is respectively in the scope of 0.001-0.8%, by normal casting, rolling or forge step after solution heat treatment after, cool off in 880-930 ℃ of time-out, and described steel was kept 5-60 minute under same temperature.
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